It is known to form microelectronic packages that include an integrated circuit die and are attached to printed circuit boards by solder interconnections to form microelectronic assemblies. The solder interconnections physically attach and electrically connect the integrated circuit die to the printed circuit board to facilitate transmission of electrical signals to and from the integrated circuit die for processing. One type of microelectronic package, referred to as a ball grid array (BGA) package, comprises an integrated circuit die mounted on a carrier that is in turn attached to a printed circuit board by solder interconnections. The carrier is expensive and increases the footprint and profile of the microelectronic package and the printed circuit board and, consequently, the size of the microelectronic assembly.
Another technique for attaching an integrated circuit die to a printed circuit board is referred to as direct chip attach, known as DCA. In DCA, an integrated circuit die is directly attached to a printed circuit board. This technique reduces the area needed on the printed circuit board by eliminating the carrier used in BGA packages. However, because of the small size of the solder bumps on the integrated circuit die, typically having a diameter less than 125 microns, an underfilling encapsulant is needed to support and protect the solder interconnections. The process of underfilling the integrated circuit die is time-consuming, and there are difficulties associated with ensuring that the entire integrated circuit die is underfilled. Further, due to the small size of the solder interconnections, it is difficult to test the integrated circuit die prior to attachment to the printed circuit board. If the integrated circuit die is found to be defective after attachment to the printed circuit board, the integrated circuit die and the encapsulant have to be removed from the printed circuit board and replaced. This rework is time-consuming and expensive.
Therefore, a need exists for a low-cost microelectronic assembly wherein an integrated circuit die is connected to a printed circuit board by solder interconnections to form a low-profile microelectronic assembly and wherein the area of the printed circuit board required to attach the integrated circuit die is reduced. Further, a need exists for a microelectronic package that facilitates testing of the integrated circuit die before the integrated circuit die is attached to a printed circuit board.